In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicants expressly reserve the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention.
Materials have chemical, microstructural, and mechanical properties that are a function of composition and processing. While materials will have a composition within specified ranges and/or have a specified processing method, the specification does not always state or put limits on specific interstitial constituents (such as C or N) or specific processes that influence every desired property of the material. Furthermore, even when a material is within a specification, there is source-to-source and heat-to-heat variability in the composition of the material, which may lead to variability in properties to be outside of acceptable limits and/or tolerance bands.
This variability applies, for example, to the materials and methods used in welding. As an example, ERNiCr-3 (a grade of welding wire also known as Filler Metal 82) is widely used for joining dissimilar metals via fusion welding and is commonly found in, for example, the nuclear power industry for dissimilar metal welds in pressurized water reactor components. ERNiCr-3 can be sourced from various manufactures and, while ERNiCr-3 from each manufacturer will be compositional within specification, the material specifications and manufacturing methods for these materials do not control nitrogen content or nitride formation except through the control of bulk concentrations of constituent elements and there is variability in material content and material performance due to localized variability in composition whereby the ERNiCr-3 material still exhibits a wide range of chemical, microstructural, and mechanical properties.
These unspecified compositional variations can impact the performance of the weld material joining the two metallic bodies forming a weldment, as well as the weldment overall. For example, variations in constituents not covered by the specification alone or in combination with narrower ranges for constituents covered by the specification for various fusion welding processes and materials can influence formation of precipitates within inter-dendritic and inter-granular sites of the weld microstructure and can have an influence on the material properties (among other things, weld crack susceptibility) and result in performance variability.